ENGLEWOOD, Colo. (AP) Vance Joseph's decision to tuck his red challenge flag back into his pants pocket loomed large until the Denver Broncos pulled off a last-second win over the Los Angeles Chargers.

Still, the failed 2-point conversion early in the fourth quarter of Denver's 23-22 last-second win highlighted a loophole in the NFL rule book that Denver's coach said Monday he'd like to see closed.

Line judge Jeff Seeman ruled Case Keenum came up short on a 2-point draw following Phillip Lindsay's touchdown run that put Denver ahead 20-19 with 12 minutes left, and Joseph said one of the officials told the quarterback his team should challenge the call because it was so close.